Implantable medical devices (IMDs) include devices implantable in a mammalian body that sense medical parameters, monitor medical conditions, administer therapy, or any combination thereof. Typical IMDs include a variety of electrical and/or mechanical components, often including a housing that houses the components. Because the components may be fragile, the housing is usually sufficiently robust to protect the components from forces to which they would otherwise be exposed when implanted within the body. Housings may be constructed from titanium, for example. In order to avoid potentially harmful interactions between the components and bodily fluids, such as corrosion, IMD housings are typically hermetically sealed.
Large components common to most IMDs typically include a battery, a coil, and a hybrid circuit that includes digital circuits, e.g., integrated circuit chips and/or a microprocessor, and analog circuit components. IMDs may include other components as well. The components and the housing each add bulk to the IMD.
Some medical devices may be implanted in the head of a patient. For example, an IMD may be implanted under the scalp and on top of the cranium, with one or more leads deployed on the head or implanted in the brain. In many cases, the implantation is not permanent, and it may be advantageous to remove the device for reasons such as repair, maintenance, replacement, or because the patient no longer benefits from the device.